Manufacture of esters of the borneols



Patented Apr. 22, 1930 UNITED STATES PATENT OFFICE KARL STEPHAN AND FRITZ ULFFERS, F BERLIN-CHARLOTTENBURG, GERMANY, AS-

SIGNOBS TO SCHERING-KAHLBAUM AK TIENGESELLSCHALFT, OF BERLIN, GERMANY MANUFACTURE OF ESTERS OE THE BORNEOLS No Drawing. Application filed March 30, 1926, Serial No. 98,625, and in Germany April 11, 1925.

Our invention refers to the manufacture of esters of the borneols (i-soborneol and borneol) from camphene in the presence of catalytic acids.

It is known that camphene can be transfcrmed into isoborneol esters admixed with borneol esters by means of fatty acids, for example acetic acid, when using as catalysis strong mineral acids (for example sulphuric acid, nitric acid or hydrochloric acid) and that the corresponding alcohols can be obtained therefrom by saponification. The esters obtained are, however, not pure because strong mineral acids in secondary reaction attack both the camphcne and the esters. This affects both the purity and the yield of isoborneol;

Esters of substantially greater purity and from them isoborneol of substantially higher melting point can be obtained when according to this invention there is employed, in place of mineral acids, acids of less acidity, such as pyrophosphoric acid. y 7

The attachment of the fatty acids takes place both more quickly and more completely when they are added in'q'uantities which are in excess of that theoreticallynecessary. The same object may also be obtained by the use of highly concentrated fatty acids.

The reaction takes place extraordinarily quickly.

The fatty acids employedcan be recovered easil and quantitatively from the wash waters y evaporation and heating.

The invention is illustrated in the following example, the parts being by weight 10 parts of camphene are well stirred with 20 parts of 95% formic acid and 2 arts of pyro hosphorio acid and heated to a out 60 C. he temperature rises of itself to. about 70 (1, care being taken that this temperature is not exceeded. The reaction is completed in a few minutes. The excess of formic acid is then distilled off in vacuo and the product of the reaction washed with water until neutral. The pyrosphosphoric acid can easily be recovered from the wash water by evaporation. The ester has a saponification value of about 308, corresponding to 100% isoborneol formate and a specific gravity of 1.010 at 20 C.

The product obtained has the formula t' .,H .().()(H.

lVe wish it to be understood that the production of the said esters is not limited to the 2. Process of manufacturing esters of the borneols which consists in heating highly concentrated fatty acid withcamphenein the presence of pyrophosphoric acid at about 60 C. and taking care that a temperature of C. is not exceeded, distilling off the excess of the fatty acid and washing the product of the re- 7 action.

In testimony whereof we aflix our signa tures.

KARL STEPHAN. FRITZ ULEFERS. 

